assertDictContainsSubset has been deprecated since 3.2 and is not
documented anymore, apparently because the order of its parameters is
less than obvious.
Consequently, remove the call to said dict & replace it with
assertions on item sets.
Note: the odd formatting is because these bits are literal-include-ed
in the documentation as sub-slices (just the relevant code lines), so
ideally they shouldn't be moved around and no additional content
should be added to those specific lines.
Xavier Morel